The present invention relates to a statistical multiplexer for coding and multiplexing multiple channels of digital television data.
Digital television has become increasingly popular due to the high quality video image it provides, along with informational and entertainment features, such as pay-per-view, electronic program guides, video-on-demand, stock, weather and stock information, Internet hyperlinks, and so forth. Such television data can be communicated to a user, for example, via a broadband communication network, such as a satellite or cable television network, or via a computer network.
However, due to the bandwidth limitations of the communication channel, it is necessary to adjust a bit rate of the digital video programs that are encoded and multiplexed for transmission in a compressed bit stream. A goal of such bit rate adjustment is to meet the constraint on the total bit rate of the multiplexed stream, while also maintaining a satisfactory video quality for each program.
Accordingly, various types of statistical multiplexers have been developed that evaluate statistical information of the source video that is being encoded, and allocate bits for coding the different video channels accordingly. For example, video channels that have hard-to-compress video, such as a fast motion scene, can be allocated more bits, while channels with relatively easy to compress scenes, such as scenes with little motion, can be allocated fewer bits.
However, there is a need for an improved statistical multiplexing system. Such a system should employ a number of individual encoders that encode data from a number of incoming channels of source video data. This data may be obtained from a storage media, live feed, or the like.
The system should dynamically allocate bits to the individual encoders to encode frames of video data from the channels.
The system should distinguish between an encoding bit rate allocation and a transmission bit rate allocation.
The system should assign a transmission bit rate to each video channel to prevent a mismatch between the input and output bits of a modeled decoder buffer.
Moreover, the system should check for impending decoder buffer overflow or underflow events to set minimum and maximum limits on the transmission bit rate. These limits should be set based on whether a new transmission bit rate can be implemented before the decoding time stamp (DTS) of the current or next frame.
The system should be usable with essentially any type of video data, including high-definition (HD) and standard-definition (SD) television (TV).
The present invention provides a system having the above and other advantages.